Field
Exemplary embodiments of the disclosure relate generally to aerodynamic flow control for turbofan aircraft nacelles and more particularly to translating turning vanes on the leading lip of ultra-short nacelles.
Background
Turbofan engines are widely employed for large commercial aircraft. As engines become larger and fans become wider, nacelles housing the fans must become shorter to achieve lower fuel burns. However, shorter nacelles, especially the resulting shorter inlets means that at adverse conditions such as high angles of attack or crosswind conditions the flow is more likely to separate behind the leading edge of the short inlet. The short inlet's smaller leading edge radius, and other features, makes it more difficult for flow to stay attached when airflow entering the engine must turn before heading in a direction approximately normal to the fan-face. If the flow separates at the leading-edge of the nacelle, the resulting distortion at the fan-face is undesirable. The separated flow may reduce performance, increase noise, and require heavier support structure to mitigate aerodynamically induced vibration. Existing solutions include simply making the inlet longer. Alternatively blow-in doors used earlier nacelle designs may be employed. However, making the inlet longer is not viable option in many applications as it reduces effectiveness of the larger engine by creating excess drag and weight. Blow-in doors increase emitted noise from aircraft operations and are structurally complex. It is therefore desirable to provide alternative solutions for inlet flow control which overcome the constraints of prior art solutions and provide improved performance.